Bug 833291 - Part 2/7: add thread/participant stores. r=hsinyi, a=tef+
Bug 833291 - Part 3/7: fix saveRecord(). r=hsinyi, a=tef+
Bug 833291 - Part 4/7: fix deleteMessage(). r=hsinyi, a=tef+
Bug 833291 - Part 5/7: fix markMessageRead(). r=hsinyi, a=tef+
Bug 833291 - Part 6/7: fix getThreadList(). r=hsinyi, a=tef+
Bug 833291 - Part 7/7: fix createMessageList(). r=hsinyi, a=tef+